When persons pretend to be friends on a regular basis so often that they actually develop a small friendship, even though they can't stand eachother. People will do this for any number of reasons, though commonly it is done to avoid drama or an ass kicking.

Chris - Dude, Abe is such a herb, you're friends with that guy?
James - Meh, it's more of a forced friendship, he's always down to be the designated driver.
Chris - What a tool!